Recently, color image printing is spread in the field of copying machines and printer and demand for high image quality is raised on the market.
Color toners to be used in the copying machines and printers are required to have not only high color reproducibility but also high reliability, concretely stable electrostatic chargeability for stably for forming image density without dependency on humidity; cf. JA-A H05-019536.
All colors can be principally reproduced by color mixing of the subtractive primaries of yellow, magenta and cyan. However, in the case of practically forming a color image by color toners each containing an organic pigment, the reproducible gamut of color capable of being reproduced is limited sometimes according to the spectrographic properties of the organic pigment dispersed in a binder resin and the color mixing ability when the different color toners are overlapped. Therefore, the color of the original image tends to be difficultly reproduced in the practical use; cf. JP-A H09-166889.
Additive color synthesis using three color primaries of red, green and blue is principally advantageous for extending the reproducible color range, and the reproducible color range by the electrophotographic printer is left within the range of printing standard of Japan Color as against the color range standard s-BGR for displays for personal computers relating to internet. Therefore, a problem is caused that the color range of the display cannot reproduced by the printer; cf. JP-A 2005-196018.
Moreover, JP-A 2005-221891 discloses a toner containing a near-infrared radiation absorbent and a fluorescent whitening agent. However, the object of this toner is to form an invisible image not affecting a visible image and not to improve the color reproducibility in the visible image.